Movment in bores - engine done 20thou from re-build
14-12-2004, 10:00 PM
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Movment in bores - engine done 20thou from re-build
One simple easy (i hope) question;
On an engine thats done 20 thou, runs fine etc....
should there be a small amount of movement when the pistons are up flat against the top of the block???
I was always lead to belive that there should be a small amount of play for when the engine heats up to operating temps?
On an engine thats done 20 thou, runs fine etc....
should there be a small amount of movement when the pistons are up flat against the top of the block???
I was always lead to belive that there should be a small amount of play for when the engine heats up to operating temps?
15-12-2004, 02:45 AM
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Yes, the aluminum pistons have a different coefficient of thermal expansion (CTE) than the bores so they need room to expand. Even when they are up to temperature, there is still a LITTLE room, otherwise the pistons would seize in the bores.
The trick is to get the clearances JUST RIGHT
The trick is to get the clearances JUST RIGHT
15-12-2004, 05:05 PM
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I've got my new pistons sitting here on my desk for the rally car and I"ll be dropping them off at the machine shop on my way home from work. The sheet that comes with them says that I need 0.0030" clearance, so that gives you the idea of how much bigger the bore is than the piston.
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15-12-2004, 05:37 PM
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Got told the engine wasn't worth fook all, as there was play in the pistons (which you could only get if you put both thumbs on each one and tried to rock them backwards and forwards)
Got 1/3rd of the asking price for it
Well, lesson learned
Got 1/3rd of the asking price for it
Well, lesson learned
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